Aircraft with rotary and fixed wings



P. J. PAPADAKOS AIRCRAFT WITH ROTARY AND FIXED WINGS Jan. 12, 1954 FiledDec. 19, 1950 .11 Sheets-Sheet 1 ATTORNEY P. J. PAPADAKOS AIRCRAFT WITHROTARY AND FIXED WINGS Jan. 12, 1954 ll SheetsSheet 2 Filed Dec. 19,1950 ATTORNEY Jan. 12, 1954 P. J. PAPADAKOS AIRCRAFT WITH ROTARYANDFIXED WINGS ll Sheets-Sheet 3 Filed Dec. 19, 1950 IN V EN TOR. PE 75J: 1 44/ 140)? 05 m Jan. 12, 1954 P. J. PAPADAKOS AIRCRAFT WITH ROTARYAND FIXED WINGS Filed Dec. 19, 1950 11 Sheets-Sheet 4 ww @w hm ATTORNEYJan. 12,1954 P. J. PAPADAKOS 2,665,859

AIRCRAFT WITH ROTARY- AND FIXED WINGS Filed Dec. 19, 1950 11Shegats-Sheet 5 Jan. 12, 1954 P. J. PAPADAKOS v AIRCRAFT WITH ROTARY ANDFIXED WINGS l1 Sheets-Sheet 6 Filed Dec. 19, 1950 3nbentor Gttorneg Jan.12, 1954 P. J. PAPADAKOS AIRCRAFT WITH ROTARY AND FIXED WINGS l1Sheets-Sheet '7 Filed Dec. 19, 1950 N Y iii 3nventor P5767? J: [WP/1014A05 attorney Jan. 12, 1954 Filed Dec. 19, 1950 xvw . 3nventor PETE/P \T.MPH UPI/(0S attorney Jan. 12, 1954 P. J. PAPADAKOS 25665359 AIRCRAFTWITH ROTARY AND FIXED WINGS Filed Dec. '19, 1950 v 11 Sheets-Sheet 9 a72 7i i 0 ag a 7 saw @000 I fi 73 1 76 77 74 72 i inventor PETE/i a?P4P40/7K05 I (Ittomeg P. J- PAPADAKOS AIRCRAFT WITH ROTARY AND FIXEDWINGS Jan. 12, 1954 ll Sheets-Shet 10 Filed Dec. 19, 1950 (Ittomeg 1954P. J. PAPADAKOS 2,665,859

AIRCRAFT WITH ROTARY AND FIXED WINGS Filed Dec. 19, 1950 ll Sheets-Sheetll INVENTOR PETE/P JI FHPAIBMOS ATTORNEY Patented Jan. 129 1954 AIRCRAFTWITH ROTARY AND FIXED WINGS Peter James Papadakos, Brooklyn, N. Y.,assignor to Gyrodyne Company of America, Inc., New York, N. Y., acorporation of New York Application December 19, 1950, Serial No.201,628

The present invention relates to aircraft and more particularly toaircraft having both fixed and rotary wings.

Helicopters have many desirable characteristics, in particular theirability to hover, to fly in any direction and to rise and descendvertically so that they can land virtually anywhere and can take offwithout any prepared airstrip. However, they have the disadvantage oflow speed and poor performance in forward flight. Fixed wing aircraftare capable of higher speed and have better performance in forwardflight but are less maneuverable and require a runway of suitable lengthfor taking off and landing.

It is an object of the present invention to provide a convertoplane, i.e. an aircraft having the desirable characteristics of a helicopterdurin take-off and landing and the desirable characteristlcs of a fixedwind aircraft in forward flight.

The aircraft in accordance with the present invention comprises afuselage, coaxial contrarotating rotors above the fuselage, fixed wingsprojecting laterally from the fuselage, twin engines carried in enginecells on the Wings and propellers providing thrust for forward flight,the engines being arranged to drive alternatively or simultaneously boththe rotors and the propellers. During take off, landing and hovering,one hundred per cent of the engine power can be used for driving therotors to provide vertical lift. In forward night, 75% to 90% of theengine power can be used for driving the propellers. The necessarythrust for forward flight is thus provided more eihciently by thepropellers instead of by tilting the Whole aircraft to provide ahorizontal component of rotor lift, as in the conven-- tionalhelicopter. The pilot is afforded full control of the aircraft at alltimes by controlling the speed and pitch of the rotors, both cyclicallyand non-cyclically, by controlling the pitch of the propellers and bythe manipulation of movable control surfaces for controlling theaircraft in forward flight. The operating characteristics of theaircraft in accordance with the present invention differ from those ofboth the helicopter and the fixed wing aircraft, combining the betterfeatures of both types while eliminating undesirable characteristics.

During take-offs and landings and at low speed, the aircraft inaccordance with the invention performs as a helicopter. For fasterforward flight, increased power is applied to the propellers and thefixed wing pick up lift, thereby unloading the rotors. As the speedincreases, the

' Claims. (Cl. 2447) control of the aircraft is taken over more and moreby the movable control surfaces, as in an airplane. Thus, the aircraftgradually converts" from a helicopter to an airplane as its forwardspeed increases. When the transition is complete, the major portion ofthe lift is carried by the fixed wings and the rotors function only foradditional control. The speed limit is reached only when the thrust isequalled by the drag, as is the case with all airplanes, and is notlimited by blade stall, as is the case with helicopters.

The objects and advantages of the invention will be further understoodfrom the following description of a preferred embodiment shown by way ofexample in the accompanying drawings, in which:

Fig. lis a perspective view of an aircraft in accordance with theinvention.

Fig. 2 is a front elevation.

Fig. 3 is a side elevation.

Fig. 4 is a plan.

Fig. 5 is a schematic side elevation of one of the engine nacelles.

Fig. 6 is an enlarged plan, partly in section, of the transmission unitin the forward part of the engine nacelle shown in Fig. 5.

Fig. 7 is a plan, partly in section of a gear box at the base of therotor shafts, the section being taken on the line B'B in Fig. 8.

Fig. 8'is a vertical section on the line AA in Fig. 7.

Fig. 9 is a schematic side elevation of the interiorof the forwardportion of the fuselage, showing pilot controls.

Fig. 10 is an elevation of the rotor head.

Fig. 11 is a plan of the rotor head. i Figs. 12, 13 and 14 areperspective, plan and front elevation of another embodiment.

The aircraft shown in the drawings comprises a fuselage l surmounted bya rotor head 2 having an upper rotor 3 and a lower rotor i, fixed wings5 projecting from'the sides of the fuselage carrying nacelles 6 havingengines which drive both the rotors 3 and 4 and also propellers 7 whichprovide thrust for forward propulsion and a control and stabilizingempennage comprising horizontal stabilizers 9, vertical stabilizers It,elevators Hand rudders l2. The aircraft is also provided with suitablelanding gear shown in the form of main wheels l3 and a caster nose wheelId.

The fuselage I is relatively short and compact. In the embodiment shownin the drawings, Figs. 1 through 11, thelength of the fuselage isapproximately equal to the span of the fixed wings 3. and to the radiusof the rotors. This compactness is permitted by the fact that no tailrotor is required and, moreover, the empennage 8 can be relatively closeto the wing since the control provided by the elevators II and ruddersi2 is supplemented by that provided by the rotor system so that a longlever arm is not needed. Since the rotors are driven by the outboardengines in nacelles 6, the interior of the fuselage is whollyunobstructed except for the rotor shafts and, hence, is available forpassengers and cargo. The wings and the lower portion of the fuselageare preferably made watertight so that the aircraft is amphibious. Inthis connection, it will be noted that, since the propellers I are notturning during take off or landing, they will not be damaged whenlanding on water, even though the engine nacelles are mounted low. Theoutboard mounting of the engines makes it possible to soundproof thefuselage effectively.

The wings 5 comprise a central wing section [5 that projects to bothsides of the fuselage and outer wing sections 16 that extend beyond theengine nacelles 6. The outer wing sections to are preferably foldable tothe position shown in dotted lines in Fig. 2 and may be provided withailerons l1. While a low wing construction is shown, the wings may, ifdesired, be mounted higher on the fuselage and the engine nacelles,instead of being approximately centered, may be mounted above or belowthe wings, if desired. It will be noted that the wing span isconsiderably less than the diameter of the rotors, being preferably 50to 75% of the rotor diameter.

An engine 20 is mounted in each of the nacelles 6, being supported by anengine mount ring 2! and ajforward engine mount 22. The engine is cooledby a fan 23. While the engines are shown as being internal combustionreciprocating engines of the radial type, other suitable engines may beused, as, for example, opposed cylinder pancake engines or turbines.

Each engine is coupled by a flexible coupling 24 to the input shaft 25of a transmission unit 26 disposed in the forward portion of the nacelle(Fig. 5). The transmission units 26 provide for selectively driving thepropellers and the rotors so that engine power may be applied to eitheror both. Moreover, provision is made for driving the rotors at either oftwo gear ratios and for changing from one gear ratio to the other duringThe construction of the transmission units is shown in Fig. 6. Thepropeller l is driven through a bevel gear 21 carried by a collar 23which is fixed on the inner end of the power input shaft 25, for exampleby being keyed or splined thereon. The bevel gear'zl meshes with oneormore bevel pinions 29 rotatably supported on a cage 38 which in turn isrotatable about the axis of the input shaft and carries a brake drum 3%adapted to be releasably held by a brake band 32. The pinion or pinions29 mesh with a bevel gear 33 carried by a collar 34 fixed to the propeller drive shaft 35 which is coaxial with the input shaft 25 and onwhich the propeller l is mounted. When the cage 30 is held by the brakeband 32, the propeller drive shaft is driven through the gear 21, 29 and33 which are designed to give any gear reduction or increase desired.When the brake band is released, no power is transmitted to thepropeller.

Power is transmitted to the rotors through a bevel gear 31 carried by acollar 38 fixed on the power input shaft 25 and meshing with the innerrotors both cyclically and, non-cyclically.

of two pinions 39 and 40 which are secured to one another so as torotate together, being rotatably supported on a cage 4| which in turn isrotatable about the axis of the input shaft 25. Preferably, there aretwo or more pairs of pinions 39, 4B distributed around the cage M whichis fixed to a hollow shaft 42 that surrounds, and is coaxial with, theinput shaft 25. The inner ph1 ion 39 meshes with a bevel gear 43 that isrotatable on the shaft 42 and is fixed to a brake drum 44 adapted to bereleasably held by a brake band 45. The outer pinion 40 meshes with alarger bevel gear 46 that is rotatable coaxially with the input shaft 25and is fixed to a brake drum adapted to be releasably held by a brakeband 41. On the inner end of the shaft 42, there is fixed a bevel gear49 meshing with a larger bevel gear 50 fixed on a power output shaft 5!which is disposed at right angles to the power input shaft 25 andtransmits power to the rotors. The two brake band type clutches 45 and48 are interconnected so that either may be engaged but not both atonce. When neither of the clutches is engaged, no power is transmittedto the rotors. When one or the other of the clutches 45, 48 is engaged,power is transmitted to the rotors at a gear ratio depending on which ofthe gears 43, 46 is held stationary. V

The output shafts 5! of the two transmission units 2b in the enginenacelles are connected by torque tubes 52 extending through the centralwing section i5 (Fig. 2) to a rotor transmission unit 53 rotateddirectly below the rotors and preferably mounted below the floor of thecabin in the fuselage i. As the transmission 53 is symmetrical about thelongitudinal central plane of the fuselage, one half only of thetransmission is shown in detail in the drawings (Figs. 7 and 8). Thetorque tube 52 is connected through a free wheeling unit 54 to a stubshaft 55 on which there is mounted a rotor brake disc 55. A bevelgearfi'i on the shaft 55 meshes with a larger bevel gear 58 on a shaft59 which is rotatable on an axis that is radial to the vertical axis ofthe rotors. The inner end of the shaft 59 carries a smaller bevel gearGB that meshes with a bevel gear ring 8! fixed on the lower end of aninner tubular shaft 52 on which the upper rotor 3 is mounted and alsomeshes with a bevel gear ring 63 fixed on an outer tubular shaft 6 onwhich the lower rotor l is mounted. It will be seen that the arrangementshown provides a gear reduction andalso that the two rotor shafts 62 and64 are positively driven at equal speeds in'opposite directions. Thefree wheeling units 5% permit autorotation of the rotors in the event ofengine failure and also permit both rotors to be driven by one of theengines in the event the other fails.

The propellers l are of variable pitch and preferably reversible, eachbeing controlled from a control unit 5'! (Fig. 5) mounted in the enginenacelle and connected to the propeller by a line 88. The rotors 3 and 4are also of variable pitch, provision being made for varying the pitchof the The cyclical pitch control of the rotors provides fore and aft,and also lateral, control of the aircraft. The non-cyclical pitchcontrol includes collective pitch variation of both rotors in the samesense for ascent or descent and also differential variation of the tworotors in opposite senses for directional control, i. e. steering, byvirtue of the torque differential of the rotors while their combinedlift remains substantially the same.

The various controls are illustrated in Figs. 9,

10 and 11. These figures also show the construction of the rotor head.The rotors are of the semi-rigid type. Each has a hub portion 70 whichsurrounds the rotor shaft and is pivotally connected to the shaft so asto have limited rocking movement about an axis that is perpendicular toa plane defined by the rotor shaft and the rotor blades. Shank portionsll are rotatably held in the opposite end portions of the hub, the axesof the shanks being fixed relative to the hub and forming a slightdihedral relative to one another. The outer end portion I2 of each shankis forced to receive the butt end of the rotor blade I3 which isattached by a pin I l. The drag and anti-drag forces on the blade aretaken by a bracket I5 and drag link 76. The shank portion II of eachblade is provided with a pitch control horn for rotating the shankrelative to the hub to change the pitch of the blade.

The pitch control horn I1 is connected by a link 18 to one side of aC-shaped cross-bar I9 which extends around the rotor shaft and ispivotally connected to diametrically opposite sides of a collectivepitch collar 80 which rotates with the rotor shaft and is slidableaxially of the shaft. At a point approximately opposite the link IS, thecross-bar I9 is connected by a link 3| to a universally tiltable swashplate 82. As the rotor turns, the swash plate 82 provides for cyclicalpitch variation of the rotor blades, de-

pending on how the swash plate is tilted. The connection of the pitchcontrol horns T! with the swash plate through the scissors-like,crossbars l9 pivotally carried by the vertically slidable collectivepitch collar 80 provides for the introduction of collective pitchcontrol since the pitch of the wing will be determined by the combinedeffect of the swash plate 82 and the collective pitch collar 80.

Provision is made for moving the collective pitch collars 80 of the tworotors, either in the same direction for cumulative pitch variation, orin opposite directions for differential pitch variation of the tworotors. The collective pitch collar 80 of the upper rotor is movablevertically by being connected to a rod 83 which extends down inside therotor shafts and is connected at its lower end to a rocking lever 84(Fig. 9) pivoted at 85. The other end of the lever 84 is connected by alink 86 to a differential collective pitch mixing lever 8! which ismounted for both rocking and translatory vertical movement. Thecollective pitch collar 80 of the lower rotor is connected by a rod 88,rocking lever 89 and rod 90 to the opposite end of the differentialpitch mixing lever 81. An upwardly projecting arm on the lever 81 isconnected by a link 9| to a differential collective pitch screw jack 92operated by cables 93 from rudder pedals 94. Operation of the rudderpedal acts through the screw jack 92 to rock the differential collectivepitch mixing lever 81 about its pivot and thereby mov one of thecollective pitch collars 80 upwardly while moving the other down tochange the pitch of the two rotors in opposite senses. The diii'erentialcollective pitch mixing lever 81 is also movable vertically by means ofa collective pitch screw jack 85 which is operated by cables 96 from acollective pitch control stick 9'! alongside the pilots seat 98.Operation of the collective pitch control stick 9! acts through thescrew jack 95 to raise or lower th differential collective pitch mixinglever 8'! and thereby change the pitch of the two rotors in the samesense.

The swash plates '82 of the two rotors are connected by a plurality ofrods I00, so that they always tilt together. The tilting of 'the swashplates 82 is controlled by means of a fore and aft cyclic screw jack IOIoperated by cables I02 from a cyclic pitch control stick I03 in front ofthe pilots seat and a lateral cyclic screw jack I04 connected by cablesI05 to the control stick I03 so that fore and aft movement of the stickoperates the fore and aft cyclic screw jack l0l while lateral movementof the stick operates the lateral cyclic screw jack I04.

The control of the movable control surfaces of the aircraft, namely theelevators l I, rudders I2, and ailerons I1, is coordinated with thecontrol of the coaxial contrarotating rotors described above. Thus, thecables I02, which are actuated by the stick I03 to operate the fore andaft cyclic screw jack I 0|, are connected by cables I06 to the elevatorsII. Likewise, the cables 93 that are actuated by the rudder pedals tooperate the differential collective pitch screw jack 92 are connected bycables I01 to the rudders. The stick 103 is also connected to theailerons I! so that lateral movement of the stick operates the ailerons.Additional controls provided for the pilot include a toe brake I08,throttle I09 and controls for the three brake band clutches 32, 45 and4'! (Fig. 6) and for the pitch of the propellers I.

In take off, hovering and landing, the brake band clutch 32 (Fig. 6) isdisengaged so that the propellers I do not operate while one or theother of the clutches 45, ll-depending on the desired gear ratio-isengaged to supply full engine power to the rotors. Control is providedby varying the pitch of the rotor blades cyclically, collectively anddifferentially by means of the controls described and shown (Fig. 9).For forward flight, the clutches 32 are engaged to drive the propellersI and thereby provide a forward 7 thrust. Hence, not having to tiltforwardly for forward flight like a helicopter, the aircraft inaccordance with the invention remains substantially level so that theincreased drag characteristic of a helicopter is avoided. The levelattitude of the aircraft also avoids the negative lift on the fuselagethat occurs in a helicopter by reason of its having to tilt forwardlyfor forward flight.

As'the speed of a helicopter is increased substantially above 100 milesper hour, an increasing portion of the retreating blade is in a regionof negative relative wind velocity and, in order to sustain theaircraft, the pitch of the retreating blade must be greatly increased.Finally, this angle of attack of the retreating blade becomes so largethat blade stall occurs, preventing any further increase in forwardspeed. Before full blade stall occurs, there is a periodic tip stalleffect which is responsible for much of the vibration troublesencountered during high speed helicopter flight. The flightcharacteristics of the aircraft in accordance with the present inventionare quite different. Forward thrust is provided by the propellers I and,as the forward speed is increased, the fixed wings sustain an increasingproportion of the total aircraft weight. As the demands on the rotor arethus progressively decreased, the danger of blade stall is diminished.By proper selection of wing area and incidence angle, it is thuspossible to avoid blade stall for all expected flight conditions. tivepitch requirements of the rotors decrease, instead of increase, athigher speeds, the aircraft in accordance with the invention is smootherin Since the collec-' ppe'ration, more eflicient andrsarer at higherspeeds. The proportionment lrifnpower ssupplied .to :the apropllers andthe :Io'tors, :otespectively, is controlled by.thezrespectiverpitches:andlhy the gear :ratio selected :fcrfthe :rotordrive. In iast forward'fiighuia'smuchzas 7:5 .to290.% :oi ;the;enginepower is delivered to .-the;pr.opellers.

"The :aircraft in accordance with the :present inventionthus. has:therfollowing rcharacteristics I 1. The danger 10f motor :lolade stall,.with 1consequent adverse eirects =upon :stahility ;and;maximum: speed,is:eliminated:bymnloading'itheirotor :through: the lift-.provided:bythe'wings inziorwar'd iiight and by? utilizingitherprop'ellers:for;horizontalithrust.

:2. '..The level'flight. attituderof the aircraft aeliminatesinegativeviiuselagezliit and afiords greater fiightlcomjort. l

1:3. There' isznoasudden'loss of rotor-R. in the event'ofeng'ine failureduring :forward flight shrceztnetaircraftsflies with-a lowrbladeipitch.

-14. Objectionable .zlateral azimuth -forces, :both steady:and vibratoryarea eliminatedibyrreasoniof the cancellation of such forces with :acoaxial rotor system.

t5. With Ethe :rigidly'rinterconnected type of rotor, correctlyi'preconed and I having the cyclic andtcollective pitch :axesecoincident,:an advantage is gained in that blade structural deflection,VibIatlOHTdHEEtOICOI'iOIiS efiects,:and;control feed- :backforcesaareareiluced.

6.1The :reduction 'nf cbladexfiapping and the availability ofsaerodynamic ziiamping :from :the propellers considerably increasescstability ain :iorward lfli'ght andxresults .imsmoothness of vflight.

Z7 Automatic locks :are :preferably provided to preventrntorbla'deifiapping ?at low: rotonspeeds -m'd therebyceliminate ctheidangeri'of damage l due toiunrestrictedtfiapping duringllanding warmeup'andl idling.

i8. iWitlrthe rigidly interconnectedtype orrrotor, the :possibility ofground :resonance? is :eliminated.

29. :Contrarotating :IOtOIST neutralize torque :reactions-onthefifuselage, thus eliminating troublesomeandsometimescdangerous,inertiaaand torque *efiects, :or groundlooping,":during:,guicki starts cormtops 'ofzthe. motor.

10. The greater kinetic energy of the coaxialrotorisystemmermitszverticala descentratra; much slower:rate-:duringpower-off landings. n. .The reduced lblade {pitch :reguirementcharacteristic cof 'theiaircraft in forward Hflight effectively :reducesrperioiiicfltipstall. Consequentlygvibratiomfrom,this source is reducedand WhatI:claim-anddesire to secure by Letters Patent is:

11. Aircraft :comprising iarfuselageyfixed wings projecting laterally.:fr.om the fuselage, engines carried on said wings and spaced from thefuselage, propellers 'for forward propulsion associated respectivelywith and adapted to be drivenlby said engines, a rotor head surmountingthe fuselage and comprising axially spaced, contrarotatingcoaxialrotors, coaxial shafts carrying said rotors and extending downwardlyfrom the rotors, a central transmissionconnected to said rotorshafts'for driving said rotor shafts at equal speed-inoppositedirections, a transmission unit disposed adjacent and :connected to eachengine andaitorgueztube connecting each of said latter transmissionunits to the central transmission to provide drivingiconnections betweeneach engine and both rotors, said transmissions comprisingmeansiorsselectively coupling each engine to both of said rotors and tothe propeller associated with the-engine.

2.,Aircraft comprising a fuselage, fixed wings projecting laterally fromthe fuselage, engine nacelles carried .on said wings and spaced from thefuselage, an engine in each of said nacelles, a propeller associatedwith and adapted to be driven by each eenginaasingle rotor headsurmounting the fuselage and comprising axially spaced, contrarotatingcoaxial rotors, transmission means interconnectingsaid rotors andengines for selectively connecting each of said engines with both rotorsto drive said rotors from tthecalternating:stresseszonflthe blades andihub arezless. I l

1While.:an embodiment'of the presentinvention :haszbeendescribed;inidetail,iit will-be understood thatthis is only hy away 'ofexample sand that modifications ;may zbe'zmad within the :scope of theinvention. Thus, for-example, asillustrated :in Fig. 12, pusher-type;propellers may lce :usedand pthelzrotor transmissionmaybelocated-at-ithe top,

ratherthan-at therbottom,'of the:.iuselage,;power from the ;outboardengines :being I transmitted means of torque tubesextendingithrough.struts lt'willrfurtherzbe:seenlthat in thiseembodiment,-theenginenacelles areirnountedahove the .fixedwings. ,Whiletwobladed;rotors have been shown,- it will be understoodthat a difierentnumber rof blades 1 can be used for the rIG'COILS as well astheipropellers. :Still othenmodifications .will occur-tea personskilledin theart-withinithe scope of .theappendedclaims.

said engines including idriving connections maintaining a fixed speedratio'between thetwo rotors and'meansconnectingsaid engines to saidpropellers'for selectively coupling and uncoupling each propeller withitsassociated engine.

3. Aircraft comprising a fuselagafixed'wings projecting laterally fromthe fuselage, engine nacelles carried on said'wings 1 and spaced fromthe'iuselage, 'an'enginein each of said nacelles, a:.prope'llerassociated with and adapted to be driven'iby each engine, a rotorheadsurmounting the 'Ifuselage and comprising variable pitch, axiallyspaced, contrarotating coaxial rotors, transmission -meansinterconnecting said rotors and engines for selectively connecting eachof said engines with both rotors-to drive-said rotors from saidenginesincluding driving connections maintaining -a iixed-speed ratio betweenthe two rotors, means interconnecting said engines and propellers forselectively coupling and uncoupling each propeller with its associatedengine and means'ior'varying'the pitch-of said rotors to vary thedistribution of power to the propellers and rotors between a limit'inwhich-substantially all thepower or both engines is delivered to therotors and'a'limit in which as much asseventy-five to ninety'per cent ofthe power of both engines is delivered 'to'the propellers, the remainderbeing delivered to the rotors. v

' 4. Aircraft comprising afuselage, fixed wings projecting laterallyfrom the fuselage, engine nac'clles carried on said wings andspaced fromthe fuselage, an engine'in'each of said nacelles, .a propellerassociated witli'and adapted to'he drivenby each engine, a. rotor headsurmounting the iuselagesand comprisingaxially spaced, contrarotatingcoaxial 'rotors, transmission means interconnecting said rotorsandengines for selectively connecting each of said engines withbothrotorsto drive saidrotors from said engines including drivingconnections maintaining a fixed speed .ratio between .the two rotors-andmeans interconnecting said engine and propellers for selectivelycoupling and uncoupling each propeller with its associated engine, saidinterconnecting means including means for varying the speed ratiobetween the propellers and the rotors.

5. In rotary wing aircraft, a fuselage, fixed wings projecting laterallyfrom the fuselage, engine nacelles carried on said wings and spaced fromthe fuselage, an engine in each of said nacelles, a propeller associatedwith each engine, a rotor head surmounting the fuselage and comprisingaxially spaced, contrarotating coaxial rotors, a central transmissionconnected to said rotor shafts for driving said rotor shafts in oppositedirections at a fixed speed ratio relative to one another, atransmission unit disposed adjacent each engine, a torque tubeconnecting each of said latter transmission units with said centraltransmission to provide driving connections between each engine and bothrotors, said transmission units comprising means for selectivelycoupling each engine to both of said rotors and 10 for selectivelycoupling each engine to the prcpeller associated with the engine, andpilot control means connected to said units for coupling and uncouplingsaid rotors and propellers in flight.

PETER JAMES PAPADAKOS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,350,456 Hewitt Aug. 24, 1920 1,783,458 Windsor Dec. 2, 19301,877,902 Kuethe Sept. 20, 1932 1,957,277 Leray May 1, 1934 2,068,617Wilford Jan. 19, 1937 2,317,340 Bennett Apr. 27, 1943 2,410,533 ThomsonNov. 5, 1946 FOREIGN PATENTS Number Country Date 616,764 France Nov. 2,1926

